Controlled force applicator

ABSTRACT

A device for applying a controlled or predetermined force at a point of contact on a surface, comprising a contact member or shoe carried on the end of a shaft, a housing member adapted to carry the shaft allowing the shaft to move along the axis of the housing, a pair of springs, in series arrangement, positioned about the shaft each adapted to act upon the shoe, (and the shaft) with respect to the housing, a spring activating means or spring selector adapted to restrict movement of one of the springs, when in closed position and to allow free movement of such spring when in an open position, a carrier means for repeatedly moving the housing toward a workpiece with the shoe contacting the surface of the workpiece and, after contact is made, to cause the housing to further descend toward the workpiece and a means for actuating the spring selector or spring-activating means. By use of the described apparatus the dead pressure, which may be of unlimited force, exerted by the carrier means to bring the applicator into contact with the surface of a workpiece, is converted to a firm, resilient force of predetermined pressure, the magnitude of such pressure being selectable.

United States Patent [72] Inventor Donald M.Husted Wilton, Conn. 121] App1.No. 22,624

122 Filed Mar. 25. 1970 145] Patented Aug. 24, 1971 [73} Assignee Ivanhoe Research Corporation New York, N.\.

[54) CONTROLLED FORCE APPLICATOR 7 Claims, 5 Drawing Figs.

[52] U.S.Cl 1l2/l21.l5, 1 12/239 [51] lnt.Cl DOSb 21/00 [50] Field of Search ..1 12/235-240,

218,121.13,l2l.ll,2,12l.l5,203, 205

Primary ExaminerJames R. Boler Att0rneyBurgess, Dinklage & Sprung ABSTRACT: A device for applying a controlled or predetermined force at a point of contact on a surface, comprising a contact member or shoe carried on the end of a shaft, a housing member adapted to carry the shaft allowing the shaft to move along the axis of the housing, a pair of springs, in series arrangement, positioned about the shaft each adapted to act upon the shoe, (and the shaft) with respect to the housing, a spring activating means or spring selector adapted to restrict movement of one of the springs, when in closed position and to allow free movement of such spring when in an open position, a carrier means for repeatedly moving the housing toward a workpiece with the shoe contacting the surface of the workpiece and, after contact is made, to cause the housing to further descend toward the workpiece and a means for actuating the spring selector or spring-activating means. By use of the described apparatus the dead pressure, which may be of unlimited force, exerted by the carrier means to bring the applicator into contact with the surface of a workpiece, is converted to a firm, resilient force of predetermined pressure, the magnitude of such pressure being selectable.

CONTROLLED FORCE APPLICATOR RELATED APPLICATION One useful application of this invention is described by Edward D. Rosenberg in his copending application Ser. No. 22,625 filed simultaneously herewith and assigned to a common assignee, under the title Drag-Steering Walking Needle Machine," the teaching of which are hereby incorporated by reference.

THE INVENTION The present invention is directed to an apparatus or device for applying a controlled or predetermined force to a spot on the surface of the workpiece.

The apparatus basically comprises a contact shoe or foot which is carried on the end of the shaft. The shaft is carried in a housing. A pair of series-positioned springs, of substantially differing strength, are carried in the housing about the shaft and selectively act upon the shoe. Normally one spring is free to travel with the housing but when a restraining lever is engaged with a collar about the shaft the free travel of the spring is restricted and the spring acts upon the shoe, with a force, related to the housing, when the shoe contacts a workpiece and the housing is moved in shoe-overriding position towards the workpiece.

As the housing overrides the normal position of the shoe, the shoe retracts into or towards the housing, and with the restraining lever engaged with the collar, both springs are compressed and exert a strong resilient force on the shoe. When the restraining lever is disengaged, only one spring is compressed and a weak, resilient force is exerted on the shoe. The restraining lever may be spring loaded so as to be normally disengaged and may be driven to an engaged position by the plunger ofa solenoid, for example, when energized or actuated.

The invention is particularly directed to the situation where the shoe is designed to repeatedly contact the surface of a workpiece or a series of workpieces for the purpose of exerting a holding action thereon, when desired. When such a holding action or force is desired the solenoid is energized and positions the biased restraining lever in collar-locking position, and the housing descends towards the workpiece so that the shoe contacts the surface of the workpiece. Upon contact of the shoe on to the surface of the workpiece, the housing further descends toward the workpiece and the shoe retreats toward or into the housing, the strong spring being compressed and exerting a strong, resilient force on the workpiece via the contacting shoe.

When it is desired to exert a force of lesser magnitude, the biased restraining lever is left positioned in its normally disengaged position; and upon contact of the shoe on to the workpiece surface by the descending housing, the shoe retreats towards or into the housing, and the weak spring is compressed against the shoe exerting a weak force on the workpiece via the contacting shoe. Thus, with the present invention a theoretically unlimited force having substantially little or no resilient characteristics may be converted into a lesser force having resilient characteristics, and the magnitude of such lesser force may be controlled by selection.

The present force applicator is usefully applied as a component of a control or feed guide means for a sewing machine or the like, wherein it is desired to exert a restraining force at a point on the surface of a workpiece being passed through the machine to cause the same to turn about the point from time to time, and thus control the direction of travel of the workpiece through the machine.

THE DRAWINGS In the drawings: FIG. 1 illustrates in side elevation view one embodiment of the force applicator in relaxed condition,

FIG. 1A is a cross-sectional view of FIG. 1 across linel A-- FIG. 2 illustrates in side elevation view the force applicator making contact with a surface wherein the force applicator applies a relatively weak restraining force,

FIG. 3 illustrates in side elevation view the force applicator making contact with a surface wherein the force applicator applies a relatively strong restraining force, and

FIG. 3A is a cross-sectional view across line 3A-3A of FIG. 3. I

DESCRIPTION Referring to the drawings, 12 represents the hollow housing component of the force applicator which includes a slot or port 13, an open end 14, and a reduced opening 15 at the other end. A shaft 16 is contained substantially within the housing. The shaft 16' includes a head 17 which is located outside the housing 12, extending beyond the reduced opening 15, and larger than the opening 15, and the shaft 16 further includes an enlarged-diameter section, 18 forming a shoulder between its extremes and a foot 20 at the extreme opposite the head 17. The shaft I6, including its integral parts, is somewhat longer in overall length than the length of the housing 12 so that the head 1 7 and the foot 20 extend beyond the extremes of the housing 1 2. Within the extremes of the housing 12 and positioned in series arrangement about the shaft 16 are two springs 22 and 24, spring 24 being substantially stiffer or stronger than spring 22. The spring 22 extends between the interior or bottom part of the top of the housing and the upper portion of shoulder 18 and normally holds shaft 16 in the housing 12. Below the enlarged portion 18 of the shaft 16 and normally butting against the lower shoulder of the enlarged portion 18 is a collar 25, which is slidably mounted on the shaft 16. The spring 24 extends between the lower part of the collar 25, and the upper part of foot or shoe 20 is slightly compressed so as to normally hold collar 25 flush against the lower shoulder of the portion 18 of shaft 16. The collar 25 has a diameter somewhat larger than the enlarged-diameter portion 18 of shaft 16, and the upper end of the collar 25 normally lies adjacent to the lower edge of the slot of port 13.

Mounted on housing 12, is a pivot housing 26 and a spring housing 27. Pivotally mounted in the pivot in the pivot housing 26 is a locking lever bar 28 which is biased by a spring 29, mounted in the spring housing 27. The locking lever bar 28 is pivotally mounted so as to communicate with the upper end of collar 25 through the slot 13, and when in communication with the collar 25, the locking lever bar limits the upward travel of the collar 25 with respect to the housing 12. Communication of the locking lever bar 28 with the upper end of collar 25 is effected by energization of the solenoid 30, which ex- 7 tends or thrusts out its plunger 31 (best seen in FIG. 3) to drive the locking lever bar 28 pivotally through the slot 13, against the bias spring 29. The plunger 31 is illustrated in retracted condition in FIGS. 1 and 2 and in extended or thrust condition in FIG. 3. The plunger is also represented by arrow 31 in FIG. 3A.

The housing 12 is coupled to an arm (not shown) by mountings or brackets 33-34 which reciprocate the force applicator toward and away from the surface 35. The force with which the force applicator is driven against the surface 35 may be essentially unlimited; however, the travel of the arm after the foot or shoe 20 makes contact with the surface is limited.

FIG. 1 and FIG. IA show the components of the force apdicated by the arrows 36, that the arm has moved towards the surface 35 effectively carrying the force applicator into contact with surface 35. The locking lever bar 28 is in biased condition such as shown in F [6. 1A, and the collar 25 is free to travel with respect to the housing 12. Since spring 24 is stronger than spring 22, as the shaft 16 moves, relative to the housing 12, spring 22 becomes compressed more than normal thereby applying a resilient pressure or force on the surface 35, via shoe or foot 20, the magnitude of the pressure being the compression strength of the spring 22.

FIG. 3 shows the solenoid 30 energized, and as seen clearly in H6. 3A, the locking lever bar 28 is pivotally moved against the biasing spring 29, through the slot or port 13, into locking communication with the collar 25. This prevents the collar 25 from travelling, relative to the housing so that when the foot comes in contact with the surface 35 and the housing is driven towards the surface, the collar rides down the shaft 16 with the housing thereby compressing strong spring 24 and applying a relatively strong force or pressure on the surface It will be appreciated that the arm carrying the force applicator may be reciprocated repeatedly thus bringing the foot or shoe 20 into contact with the surface 35. Such reciprocating action may be in synchronism with another action occurring with respect to the surface 35. The surface 35 may be the surface of a workpiece moved along a supporting surface or table. The solenoid may be selectively energized or not with each cycle or part thereof.

The solenoid may be made to follow the force applicator in its reciprocating travel, or the plunger 31 may be large and essentially cover the travel of the locking lever bar 28 as it moves with the housing 21.

The spring or compression force of the springs may be in any ratio desired. For effective operation the relative force of the upper spring 22 may be substantially less than the relative force of the lower spring 24.

The material from which the foot 20 is made is preferably material with very little resiliency or compression factor.

Although the locking lever bar 28 is shown to communicate with the collar 25 on its upper part, the collar 25 may include a slot or groove in its periphery, and the locking mechanism may be driven into such slot or groove to lock the collar, relative to the housing 12.

It will be appreciated by those skilled in the art that changes other than those suggested may be made from the embodiment shown without departing from the spirit of the invention.

What is claimed is:

1. A force applicator comprising:

a hollow housing having an open end and a partially closed end,

a shaft retained in said housing and having a head and a foot and a shoulder therebetween with the head and the foot extending from said housing,

a collar mounted on said shaft between said shoulder and said foot adapted to travel between said shoulder and said foot,

a first spring retained between said shoulder and said partially closed end of said housing and normally holding said head against the said partially closed end of said housing,

a second spring retained between said collar and said foot and normally holding said collar against said shoulder,

a slot in said housing for permitting access to said collar from the exterior of said housing, and

a locking bar adapted to enter said slot and communicate with said collar for limiting movement of said collar with respect to said housing.

2. The force applicator of claim 1, and further including:

biasing means for normally holding said locking bar out of said slot for allowing said collar to move relative to said holder.

3. The force ap licator of claim 1 and further including: biasing means or normally biasing said locking bar out of said slot for allowing said collar to move relative to said holder and,

means for overcoming said biasing means for driving said locking bar into said slot for communicating with said collar.

4. The force applicator of claim 1 where in the spring ratio between said second spring and said first spring is in the range oflO/l to 30/1.

5. A reciprocating device for applying a predetermined force at a point of contact on a surface selectively during at least part of one or more of its cycles of operation comprising:

a hollow housing,

two springs in series arrangement retained therein, one

strong and one relatively weak,

a shoe guided by said housing and adapted to be acted upon by said springs,

selector means operable upon command for causing said shoe to be acted upon the stronger of said springs,

carrier means for carrying said housing and adapted for bringing said shoe into contact with said surface and for moving said housing towards said surface a distance beyond the initial point of control of said shoe therewith, and

control means adapted to issue command to said selector means whereby when said command has been issued and said shoe contacts said surface and said holder overrides the initial point of contact, the stronger of said springs is compressed against said shoe and the dead pressure exerted by said housing and carrier means is converted to a resilient restraint pressure against said surface.

6. A reciprocating device as defined in claim 5 and in which said selector includes,

biased-spring-locking means normally biased to permit said shoe to be acted upon by said relatively weak spring and when commanded to limit movement of said strong spring relative to said housing for causing said shoe to be acted upon by said strong spring.

7. The device of claim 5 wherein the spring ratio between said springs is in the range of 10/ l to 30/ l. 

1. A force applicator comprising: a hollow housing having an open end and a partially closed end, a shaft retained in said housing and having a head and a foot and a shoulder therebetween with the head and the foot extending from said housing, a collar mounted on said shaft between said shoulder and said foot adapted to travel between said shoulder and said foot, a first spring retained between said shoulder and said partially closed end of said housing and normally holding said head against the said partially closed end of said housing, a second spring retained between said collar and said foot and normally holding said collar against said shoulder, a slot in said housing for permitting access to said collar from the exterior of said housing, and a locking bar adapted to enter said slot and communicate with said collar for limiting movement of said collar with respect to said housing.
 2. The force applicator of claim 1, and further including: biasing means for normally holding said locking bar out of said slot for allowing said collar to move relative to said holder.
 3. The force applicator of claim 1 and further including: biasing means for normally biasing said locking bar out of said slot for allowing said collar to move relative to said holder and, means for overcoming said biasing means for driving said locking bar into said slot for communicating with said collar.
 4. The force applicator of claim 1 where in the spring ratio between said second spring and said first spring is in the range of 10/1to 30/1.
 5. A reciprocating device for applying a predetermined force at a point of contact on a surface selectively during at least part of one or more of its cycles of operation comprising: a hollow housing, two springs in series arrangement retained therein, one strong and one relatively weak, a shoe guided by said housing and adapted to be acted upon by said springs, selector means operable upon command for causing said shoe to be acted upon the stronger of said springs, carrier means for carrying said housing and adapted for bringing said shoe into contact with said surface and for moving said housing towards said surface a distance beyond the initial point of control of said shoe therewith, and control means adapted to issue command to said selector means whereby when said command has been issued and said shoe contacts said surface and said holder overrides the initial point of contact, the stronger of said springs is compressed against said shoe and the dead pressure exerted by said housing and carrier means is converted to a resilient restraint pressure against said surface.
 6. A reciprocating device as defined in claim 5 and in which said selector includes, biased-spring-locking means normally biased to permit said shoe to be acted upon by said relatively weak spring and when commanded to limit movement of said strong spring relative to said housing for causing said shoe to be acted upon by said strong spring.
 7. The device of claim 5 wherein the spring ratio between said springs is in the range of 10/1 to 30/1. 